The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Hammer-drills generally include a floating rotary-reciprocatory output spindle journaled in the housing for driving a suitable tool bit coupled thereto. In operation, the spindle can be retracted axially within the housing and against the force of a suitable resilient means, upon engagement of the tool bit with a workpiece and a manual bias force exerted by the operator on the tool. A fixed hammer member can be secured in the housing, and a movable hammer member can be carried by the spindle. The movable hammer member can have a ratcheting engagement with the fixed hammer member to impart a series of vibratory impacts to the spindle in a “hammer-drilling” mode of operation. A shiftable member can act upon the spindle to change from a “drilling” mode to the “hammer-drilling” mode, and vice versa.
Multi-speed drills typically include a transmission for transferring torque between a driven input member and an output spindle. The transmission can include a shifting mechanism for changing between a low-speed mode and a high-speed mode. The vibratory impacts in the hammer-drilling mode can create axial force oscillations that can affect the shifting mechanism.